Disclosure context

About BrainCipher

Braincipher is a recently emerged ransomware group that was first observed in July 2024, operating with apparent financial motivations and targeting organizations primarily across North America and Europe. The group's origin and potential affiliations remain largely undocumented by major threat intelligence organizations, though their targeting patterns suggest a broad opportunistic approach rather than nation-state backing, likely operating as an independent entity rather than through established ransomware-as-a-service infrastructure. Their attack methodology and specific technical capabilities have not been extensively documented by CISA, FBI, or major security research firms, though their victim distribution across 44 confirmed targets spanning business services, manufacturing, technology, and healthcare sectors indicates a generalist approach to target selection rather than sector-specific expertise. No major high-profile campaigns or significant law enforcement actions have been publicly documented against this group by reputable sources, suggesting either a relatively low-impact operational scale or insufficient intelligence collection on their activities. As of current reporting, the group's operational status remains unclear due to limited public documentation from established threat intelligence sources. The group has been linked to 56 public disclosures across our corpus. First observed on a leak site on July 1, 2024; most recent post May 13, 2026. The operation is currently active.

Also tracked as: brain cipher.

Timeline of this disclosure

May 1, 2026kisnet.co.jp listed by BrainCipheron the group's public leak site

Sector and geography

This disclosure adds to ransomware activity in the Telecommunication sector, which has 54 disclosures indexed across all operators we track. Geographically, kisnet.co.jp is reported in JP, a country with 88 ransomware disclosures in our corpus.

How we know this. Darkfield monitors public ransomware leak sites continuously, archiving every new disclosure and the data later released against the victim. Each entry on this page is sourced from the operator's own publication and cross-checked against complementary OSINT feeds (RansomLook, ransomware.live, RansomWatch). We do not collect or host stolen data — only the metadata, timestamps and screenshots needed to make the public disclosure searchable and accountable. Records here are corrected when the original post is edited, retracted, or merged with another disclosure.

Ransomware victim disclosure

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kisnet.co.jp

Claimed by BrainCipher · listed 20 days ago

19d

Age

since listed · data leaked

Status timeline

Listed
May 1, 2026
Data leaked

At a glance

Group: BrainCipher
Status: Data leaked
Country: JP
Sector: Telecommunication
Listed on leak site: May 1, 2026

About the victim

AI dossier — public-source company profile

kisnet.co.jp is a Japanese telecommunications and internet services company operating under the .co.jp domain, indicating incorporation in Japan. Based on its sector classification and domain, it likely provides networking, connectivity, or ISP-related services to business or residential customers in Japan. No further detail is available from the public site excerpt.

Industry: Telecommunications / Internet Services

Attack summary

Severity: high — Over 1 TB of data has been confirmed exfiltrated and publicly published across multiple onion download links, representing significant business data exposure from a telecom provider; specific data categories (PII, financial, etc.) are unconfirmed, preventing a critical rating.

BrainCipher claims to have exfiltrated more than 1 TB of data from kisnet.co.jp and has published the data via multiple Tor-based download links, indicating full data disclosure without a stated ransom demand.

high

Data the group says was taken

AI dossier — extracted from the leak post

Exfiltrated company data (>1 TB, contents unspecified)

The group's post references roughly 10 proof files.

Original description

AI-summarised, not from the leak post

Kisnet Co., Ltd. is a Japanese internet service provider based in Japan. The company offers broadband and network connectivity services primarily to residential and business customers. Operating within the telecommunications and ISP industry, Kisnet provides internet access solutions in the Japanese market. The company is part of Japan's regional ISP sector, delivering reliable network infrastructure and related services to its subscriber base.

The leak post

captured from the group's site

We have more 1TB of data. If you think you are here by mistake, please contact us at [email protected] 
⏳ 12d 8h 29m 41s remaining 
Download: 3fg2gfwrdks46drwvejpgpak5klrflclsjjo35dxtqfk3poeez6oezad.onion If you think you are here by mistake, please contact us at [email protected] 
Download: emdnfl2fv32jhssxcbxlo6dzg2at4d7qbw2md6inz63qzdfgyln5cwyd.onion If you think you are here by mistake, please contact us at [email protected] 
Download: a4vbe7yp4kluped6khuhpr5nmzshiimx2jt5j22ozriiq6ngsm3fcpyd.onion If you think you are here by mistake, please contact us at [email protected] 
Download: x3nb7qcygpem2j5xzstyzdtgzofzkwkx4eko3ug4r73i6uhcgvyffjyd.onion If you think you are here by mistake, please contact us at [email protected] 
Download: 3frnhzcnlkjnw5q3tm6elzizinm2k3bmrtf2xwqjzpcxzeqwn2tv6wyd.onion If you think you are here by mistake, please contact us at [email protected] 
Download: 6ft2dfh26wm3w44orpjcgviutvfp25ez2iyh5ego5egvfmifrws7vvqd.onion If you think you are here by mistake, please contact us at [email protected] 
Download: zijgmuqjzb6dc7pofxhtaiz36qqyg35lhutybmzaz6whzgei2casjgid.onion If you think…

Sources

Victim sitekisnet.co.jp
Leak posthttp://vkvsgl7lhipjirmz6j5ubp3w3bwvxgcdbpi3fsbqngfynetqtw4w5hyd.onion/n/kisnet

Source

Indexed 20 days ago

This page surfaces a public ransomware disclosure indexed by Darkfield. Original posts come from the operator's own leak site; we cross-check against ransomware.live, RansomLook and RansomWatch where applicable. Share this URL freely.